The HTML characters repeat throughout the message, but not on every message, though those sent from Hotmail are typically affected (but it is not always Hotmail).

The problem is due to the email having character encoding in the charset META tag that differs from the character encoding in the MIME part and a HTML disclaimer having been added. When Exchange 2010 SP1 adds the HTML disclaimer it re-encodes the message and this results in a corrupt message because the wrong character set information is read.

The fix for this has been documented in KB969129, which refers to Exchange 2007, but the same fix is true for Exchange 2010 SP1.

The fix is to add the DisableDetectEncodingFromMetaTag attribute to EdgeTransport.exe.config. This file can be found at \Program Files\Microsoft\Exchange Server\V14\bin and can be opened in Notepad. Make a backup of the file before you change it and then add to the <appsettings> area of the file the following

<add key="DisableDetectEncodingFromMetaTag" value="true" />

After you save the config file you need to restart the Microsoft Exchange Transport service for the setting to take effect.